Effort Level Control / Claude Code v2.1.38

What

Control how much effort Claude puts into responses during a session.

Usage

claude --effort medium
claude --effort high

Details

Evidence

CLI flag definition (search for "--effort <level>")

Strings lifted out of the shipped bundle, so the claim above can be checked against them.

The build it came inv2.1.38

10 Feb 2026 · 17 entries, this one is #1.

Either side of it

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Names in this entry

settinglow
A new modelSettings config key stores an effort level per model, from low to xhigh.
settingmedium
Workflow size now defaults to medium, and an admin policy setting overrides whatever you chose.
settinghigh
The bundled Claude API skill docs now target the new Opus, covering thinking defaults, fallbacks and fast mode.
settingmax
The bundled Claude API skill docs now target the new Opus, covering thinking defaults, fallbacks and fast mode.
cli--effort
Set the effort level for the current session. Options: low, medium, high, xhigh, max, or ultracode. Available levels depend on the model. ultracode requests xhigh effort with ultracode turned on, and requires Claude Code v2.1.203 or later. Overrides the modelSettings and effortLevel settings for this session and does not persist

Is this right?

Other releases about the same thing. Found by shared names or similar wording; neither means one caused the other.